Much can be regained. Same with detox and reminerization of ones own body. With nutritional herbs and good meditation practices, all kinds of shit is possible. Having been an occultist for 15 years I can say that poison water and poison food make certain higher states of consciousness/awareness more difficult to achieve. Not to mention magick/sorcery.

Besides, with the financial aspect of biological overshoot, peak everything, and catabolic societal collapse quickening, what better investment to make than your mind/body/intelligence/longevitiy? It cannot be stolen (only ruined), has value systems not tied to fiat money, banksters, or some ponzi socioeconomic/political matrix. Other than love, security, shelter/food, and companionship, and the great work, what else is there that really matters besides health?